In an exclusive interview with "Good Morning America," Ukrainian President Volodymyr Zelenskyy said he believes the war with Russia is "closer to an end" than many believe and called on allies to strengthen Ukraine as he arrived in the United States for a week of high-stakes diplomacy.

"The plan of victory is strengthening of Ukraine," Zelenskyy said during a sit-down interview with "Good Morning America" co-anchor Robin Roberts. "That's why we're asking our friends, our allies, to strengthen us. It's very important."

Zelenskyy spoke with Roberts as he visited New York on Monday for the United Nations General Assembly this week as part of a trip to the U.S. where he has promised to present what he calls his "Victory Plan" to President Joe Biden, as well as other key American political leaders.

See more of Robin Roberts' exclusive interview with Ukraine President Volodymyr Zelenskyy and first lady Olena Zelenska at 8:30 p.m. ET Wednesday on ABC News Live and streaming on Hulu on Thursday.

Zelenskyy declined to provide details of the plan before presenting it to Biden later this week, but he made clear that it was aimed at strengthening Ukraine with the goal of forcing Russian President Vladimir Putin to negotiate on fair terms. Zelenskyy indicated he did not believe Putin was currently ready for real negotiations.

"It's not about negotiation with Russia," Zelenskyy told Roberts. "It's a bridge to a diplomatic way, how to stop the war. Only in the strong position we can push, we can push Putin to stop the war, diplomatic way."

A source close to Zelenskyy told ABC News the plan consists of five points and that its core includes specific figures and amounts of military assistance for Ukraine, as well as certain diplomatic and political steps. The plan does not include any proposed concessions to Russia, the source said, but is aimed at forcing the Kremlin to end the war.

Zelenskyy said the plan was an "urgent" one, intended to end the war quickly, not prolong it "one year, or two years or three years."

Later this week, Zelenskyy is expected to travel to Washington to meet with Biden as well as presidential candidates Kamala Harris and Donald Trump.

There are doubts a second Trump administration would continue similar levels of support to Ukraine and could perhaps push it into negotiations. Trump in the debate with Harris two weeks ago declined to say he wants Ukraine to win the war and his running mate JD Vance has said Ukraine should give up Russian-occupied territory and abandon ambitions to join NATO.

Zelenskyy said he hoped the U.S. election wouldn't influence support for Ukraine but that he understood U.S. policy could change and "therefore we need to prepare in advance."

That is why the "Victory Plan" is important, he said, saying he wants to discuss it with the candidates.

Zelenskyy again expressed gratitude to Americans and apologized for having to ask again for support.

"I'm so sorry. I know that you have your challenges. But I have to underline it and to repeat," he said. "We can't now be weak. We can't relax. Because we didn't stop Putin. Didn't stop him in his crazy ideas. That's why we have to be strong and I'm asking to understand us. And I think that we are closer to the peace than we think. We are closer to the end of the war. We just have to be very strong, very strong."

Zelenskyy also repeated his appeal to the United States to drop its restrictions on the long-range missiles they have provided to Ukraine to strike targets deep inside Russia.

Zelenskyy said he would raise the issue again with Biden again this week, saying it would allow Ukraine to strike Russian airbases used to launch hundreds of bombs into eastern Ukraine. He said he believed other allies such as France, Britain, Italy, and Germany would allow it but that the U.S. needed to lead the decision.

"But the main role is in the United States, in the president of United States, Biden. Everybody's looking up to him, and we need this to defend ourselves," he said.

Putin, meanwhile, has warned that the use of Western weapons to strike targets in Russia would mean NATO countries are at war with Russia and promised a response.

Zelenskyy's request comes amid heavy fighting in eastern Ukraine where Russia has been making steady advances in recent weeks. Russian forces are also still struggling to reverse Ukraine's incursion into Russia's Kursk region. Ukraine has said it seized hundreds of square miles and dozens of villages inside the Kursk region in the early days of its surprise offensive.

Zelenskyy told Roberts that Putin is "afraid" of the Kursk operation.

"It's true. He's afraid very much," Zelenskyy said. "Why? Because his people saw that he can't defend, that he can't defend all his territory."

Zelenskyy said Ukraine launched the surprise operation because of intelligence suggesting that Russia had been preparing to mount its own offensive into Ukraine's northern Sumy region.

"They have the desire to occupy the city of Sumy," he said. "And we decided that we need preventive steps. We had to move in with our troops. And we did it so that they did not occupy our north."

Zelenskyy also accused Russia of using Chinese satellites to photograph Ukraine's nuclear power plants, perhaps in preparation for possible strikes on them.

"The recent information is that, Russia has been using Chinese satellites and taking photos of the details of the objects on nuclear facilities," Zelenskyy told Roberts. "And in our experience, if Russia takes photos of certain objects, then there is a threat of strikes against the nuclear objects."

Zelenskyy did not say whether the Chinese satellites Russia has used were commercial satellites or controlled by the Chinese government. He said he would share information Ukraine had with leaders at the General Assembly this week.

Asked to comment on Monday, China's embassy in Washington did not respond.

Zelenskyy was joined by his wife, first lady Olena Zelenska, who is also attending events at the General Assembly.

Zelenska, who is addressing events focusing on the impact of the war on children, said she was also seeking to campaign for greater international help in returning tens of thousands of Ukrainian children deported to Russia. She said at least 19,500 remained held in Russia, but that the true number could be significantly higher.

She said so far only 308 children had been returned through negotiations, saying she hoped a 30-country coalition would find a way to do more.

"This can't carry on like this. If we are going to bring our children back at this rate, we will need more than 30 years to bring them back," she said. "So we need to bring pressure to bear to make sure they can be brought back."